[PATCH v3 ath-next 0/2] wifi: ath11k: fix HTC rx insufficient length

[PATCH v3 ath-next 0/2] wifi: ath11k: fix HTC rx insufficient length

[Miaoqing Pan]

This series of patches is to address the issue reported in
https://bugzilla.kernel.org/show_bug.cgi?id=218623.

ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1488, expected 1492
ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484

---
v2: add Reported-by tag.
v3:
 - update commit message.
 - revert the modifications to ath11k_hal_srng_dst_get_next_entry to ensure efficiency.
 - change warning to dbg when see zero-length descriptor.
---
Miaoqing Pan (2):
  wifi: ath11k: add function to get next srng desc
  wifi: ath11k: fix HTC rx insufficient length

 drivers/net/wireless/ath/ath11k/ce.c   | 38 ++++++++++++++++++++------
 drivers/net/wireless/ath/ath11k/core.h |  1 +
 drivers/net/wireless/ath/ath11k/hal.c  | 17 +++++++++++-
 drivers/net/wireless/ath/ath11k/hal.h  |  3 +-
 4 files changed, 49 insertions(+), 10 deletions(-)


base-commit: 42aa76e608ca845c98e79f9e23af0bdb07b2eb1d
-- 
2.25.1

[PATCH v3 ath-next 1/2] wifi: ath11k: add function to get next srng desc

[Miaoqing Pan]

Adding the ath11k_hal_srng_dst_next() function allows for the
separate invocation of ath11k_hal_srng_dst_peek() and
ath11k_hal_srng_dst_next() in certain situations, instead of
calling the ath11k_hal_srng_dst_get_next_entry() function alone.

Tested-on: QCA6698AQ hw2.1 PCI WLAN.HSP.1.1-04546-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1

Signed-off-by: Miaoqing Pan <quic_miaoqing@quicinc.com>
---
 drivers/net/wireless/ath/ath11k/hal.c | 17 ++++++++++++++++-
 drivers/net/wireless/ath/ath11k/hal.h |  3 ++-
 2 files changed, 18 insertions(+), 2 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/hal.c b/drivers/net/wireless/ath/ath11k/hal.c
index 61f4b6dd5380..211c085921b6 100644
--- a/drivers/net/wireless/ath/ath11k/hal.c
+++ b/drivers/net/wireless/ath/ath11k/hal.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: BSD-3-Clause-Clear
 /*
  * Copyright (c) 2018-2019 The Linux Foundation. All rights reserved.
- * Copyright (c) 2021-2024 Qualcomm Innovation Center, Inc. All rights reserved.
+ * Copyright (c) 2021-2025 Qualcomm Innovation Center, Inc. All rights reserved.
  */
 #include <linux/dma-mapping.h>
 #include "hal_tx.h"
@@ -656,6 +656,21 @@ static void ath11k_hal_srng_prefetch_desc(struct ath11k_base *ab,
 	}
 }
 
+void ath11k_hal_srng_dst_next(struct ath11k_base *ab, struct hal_srng *srng)
+{
+	lockdep_assert_held(&srng->lock);
+
+	srng->u.dst_ring.tp += srng->entry_size;
+
+	/* wrap around to start of ring*/
+	if (srng->u.dst_ring.tp == srng->ring_size)
+		srng->u.dst_ring.tp = 0;
+
+	/* Try to prefetch the next descriptor in the ring */
+	if (srng->flags & HAL_SRNG_FLAGS_CACHED)
+		ath11k_hal_srng_prefetch_desc(ab, srng);
+}
+
 u32 *ath11k_hal_srng_dst_get_next_entry(struct ath11k_base *ab,
 					struct hal_srng *srng)
 {
diff --git a/drivers/net/wireless/ath/ath11k/hal.h b/drivers/net/wireless/ath/ath11k/hal.h
index 601542410c75..317b09ec6c35 100644
--- a/drivers/net/wireless/ath/ath11k/hal.h
+++ b/drivers/net/wireless/ath/ath11k/hal.h
@@ -1,7 +1,7 @@
 /* SPDX-License-Identifier: BSD-3-Clause-Clear */
 /*
  * Copyright (c) 2018-2019 The Linux Foundation. All rights reserved.
- * Copyright (c) 2021-2022, 2024 Qualcomm Innovation Center, Inc. All rights reserved.
+ * Copyright (c) 2021-2022, 2024-2025 Qualcomm Innovation Center, Inc. All rights reserved.
  */
 
 #ifndef ATH11K_HAL_H
@@ -941,6 +941,7 @@ int ath11k_hal_srng_get_entrysize(struct ath11k_base *ab, u32 ring_type);
 int ath11k_hal_srng_get_max_entries(struct ath11k_base *ab, u32 ring_type);
 void ath11k_hal_srng_get_params(struct ath11k_base *ab, struct hal_srng *srng,
 				struct hal_srng_params *params);
+void ath11k_hal_srng_dst_next(struct ath11k_base *ab, struct hal_srng *srng);
 u32 *ath11k_hal_srng_dst_get_next_entry(struct ath11k_base *ab,
 					struct hal_srng *srng);
 u32 *ath11k_hal_srng_dst_peek(struct ath11k_base *ab, struct hal_srng *srng);
-- 
2.25.1

[PATCH v3 ath-next 2/2] wifi: ath11k: fix HTC rx insufficient length

[Miaoqing Pan]

A relatively unusual race condition occurs between host software
and hardware, where the host sees the updated destination ring head
pointer before the hardware updates the corresponding descriptor.
When this situation occurs, the length of the descriptor returns 0.

The current error handling method is to increment descriptor tail
pointer by 1, but 'sw_index' is not updated, causing descriptor and
skb to not correspond one-to-one, resulting in the following error:

ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1488, expected 1492
ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484

To address this problem and work around the broken hardware,
temporarily skip processing the current descriptor and handle it
again next time. However, to prevent this descriptor from
continuously returning 0, use the skb control block (cb) to set
a flag. If the length returns 0 again, this descriptor will be
discarded.

Tested-on: QCA6698AQ hw2.1 PCI WLAN.HSP.1.1-04546-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1

Reported-by: Johan Hovold <johan+linaro@kernel.org>
Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623
Signed-off-by: Miaoqing Pan <quic_miaoqing@quicinc.com>
---
 drivers/net/wireless/ath/ath11k/ce.c   | 38 ++++++++++++++++++++------
 drivers/net/wireless/ath/ath11k/core.h |  1 +
 2 files changed, 31 insertions(+), 8 deletions(-)

diff --git a/drivers/net/wireless/ath/ath11k/ce.c b/drivers/net/wireless/ath/ath11k/ce.c
index e66e86bdec20..ccaf9b7a6857 100644
--- a/drivers/net/wireless/ath/ath11k/ce.c
+++ b/drivers/net/wireless/ath/ath11k/ce.c
@@ -1,7 +1,7 @@
 // SPDX-License-Identifier: BSD-3-Clause-Clear
 /*
  * Copyright (c) 2018-2019 The Linux Foundation. All rights reserved.
- * Copyright (c) 2021-2023 Qualcomm Innovation Center, Inc. All rights reserved.
+ * Copyright (c) 2021-2023, 2025 Qualcomm Innovation Center, Inc. All rights reserved.
  */
 
 #include "dp_rx.h"
@@ -387,18 +387,36 @@ static int ath11k_ce_completed_recv_next(struct ath11k_ce_pipe *pipe,
 
 	ath11k_hal_srng_access_begin(ab, srng);
 
-	desc = ath11k_hal_srng_dst_get_next_entry(ab, srng);
+	desc = ath11k_hal_srng_dst_peek(ab, srng);
 	if (!desc) {
 		ret = -EIO;
 		goto err;
 	}
 
 	*nbytes = ath11k_hal_ce_dst_status_get_length(desc);
-	if (*nbytes == 0) {
-		ret = -EIO;
-		goto err;
+	if (unlikely(*nbytes == 0)) {
+		struct ath11k_skb_rxcb *rxcb =
+			ATH11K_SKB_RXCB(pipe->dest_ring->skb[sw_index]);
+
+		/* A relatively unusual race condition occurs between host
+		 * software and hardware, where the host sees the updated
+		 * destination ring head pointer before the hardware updates
+		 * the corresponding descriptor.
+		 *
+		 * Temporarily skip processing the current descriptor and handle
+		 * it again next time. However, to prevent this descriptor from
+		 * continuously returning 0, set 'is_desc_len0' flag. If the
+		 * length returns 0 again, this descriptor will be discarded.
+		 */
+		if (!rxcb->is_desc_len0) {
+			rxcb->is_desc_len0 = true;
+			ret = -EIO;
+			goto err;
+		}
 	}
 
+	ath11k_hal_srng_dst_next(ab, srng);
+
 	*skb = pipe->dest_ring->skb[sw_index];
 	pipe->dest_ring->skb[sw_index] = NULL;
 
@@ -430,9 +448,13 @@ static void ath11k_ce_recv_process_cb(struct ath11k_ce_pipe *pipe)
 		dma_unmap_single(ab->dev, ATH11K_SKB_RXCB(skb)->paddr,
 				 max_nbytes, DMA_FROM_DEVICE);
 
-		if (unlikely(max_nbytes < nbytes)) {
-			ath11k_warn(ab, "rxed more than expected (nbytes %d, max %d)",
-				    nbytes, max_nbytes);
+		if (unlikely(max_nbytes < nbytes || !nbytes)) {
+			if (nbytes)
+				ath11k_warn(ab, "rxed more than expected (nbytes %d, max %d)\n",
+					    nbytes, max_nbytes);
+			else
+				ath11k_dbg(ab, ATH11K_DBG_CE, "rxed zero-length\n");
+
 			dev_kfree_skb_any(skb);
 			continue;
 		}
diff --git a/drivers/net/wireless/ath/ath11k/core.h b/drivers/net/wireless/ath/ath11k/core.h
index 1a3d0de4afde..c8614c5c6493 100644
--- a/drivers/net/wireless/ath/ath11k/core.h
+++ b/drivers/net/wireless/ath/ath11k/core.h
@@ -128,6 +128,7 @@ struct ath11k_skb_rxcb {
 	bool is_continuation;
 	bool is_mcbc;
 	bool is_eapol;
+	bool is_desc_len0;
 	struct hal_rx_desc *rx_desc;
 	u8 err_rel_src;
 	u8 err_code;
-- 
2.25.1

Re: [PATCH v3 ath-next 2/2] wifi: ath11k: fix HTC rx insufficient length

[Johan Hovold]

On Fri, Mar 14, 2025 at 02:13:53PM +0800, Miaoqing Pan wrote:
> A relatively unusual race condition occurs between host software
> and hardware, where the host sees the updated destination ring head
> pointer before the hardware updates the corresponding descriptor.
> When this situation occurs, the length of the descriptor returns 0.
> 
> The current error handling method is to increment descriptor tail
> pointer by 1, but 'sw_index' is not updated, causing descriptor and
> skb to not correspond one-to-one, resulting in the following error:
> 
> ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1488, expected 1492
> ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484
> 
> To address this problem and work around the broken hardware,
> temporarily skip processing the current descriptor and handle it
> again next time. However, to prevent this descriptor from
> continuously returning 0, use the skb control block (cb) to set
> a flag. If the length returns 0 again, this descriptor will be
> discarded.
> 
> Tested-on: QCA6698AQ hw2.1 PCI WLAN.HSP.1.1-04546-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1
> 
> Reported-by: Johan Hovold <johan+linaro@kernel.org>
> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623
> Signed-off-by: Miaoqing Pan <quic_miaoqing@quicinc.com>

> @@ -387,18 +387,36 @@ static int ath11k_ce_completed_recv_next(struct ath11k_ce_pipe *pipe,
>  
>  	ath11k_hal_srng_access_begin(ab, srng);
>  
> -	desc = ath11k_hal_srng_dst_get_next_entry(ab, srng);
> +	desc = ath11k_hal_srng_dst_peek(ab, srng);
>  	if (!desc) {
>  		ret = -EIO;
>  		goto err;
>  	}
>  
>  	*nbytes = ath11k_hal_ce_dst_status_get_length(desc);

As I mentioned elsewhere, this function also sets the length field in
the descriptor to zero. So if there's a racing update, you may never see
the updated length.

> -	if (*nbytes == 0) {
> -		ret = -EIO;
> -		goto err;
> +	if (unlikely(*nbytes == 0)) {
> +		struct ath11k_skb_rxcb *rxcb =
> +			ATH11K_SKB_RXCB(pipe->dest_ring->skb[sw_index]);
> +
> +		/* A relatively unusual race condition occurs between host
> +		 * software and hardware, where the host sees the updated
> +		 * destination ring head pointer before the hardware updates
> +		 * the corresponding descriptor.
> +		 *
> +		 * Temporarily skip processing the current descriptor and handle
> +		 * it again next time. However, to prevent this descriptor from
> +		 * continuously returning 0, set 'is_desc_len0' flag. If the
> +		 * length returns 0 again, this descriptor will be discarded.
> +		 */
> +		if (!rxcb->is_desc_len0) {
> +			rxcb->is_desc_len0 = true;
> +			ret = -EIO;
> +			goto err;
> +		}

If you add the memory barrier and make sure not to clear the length
field above, do you still see the length sometimes always reading zero
if you retry more than once (i.e. drop the is_desc_len0 flag)?

Perhaps the device is really passing you a zero-length descriptor that
can simply be discarded straight away?

Johan

Re: [PATCH v3 ath-next 2/2] wifi: ath11k: fix HTC rx insufficient length

[Miaoqing Pan]

On 3/14/2025 4:20 PM, Johan Hovold wrote:
> On Fri, Mar 14, 2025 at 02:13:53PM +0800, Miaoqing Pan wrote:
>> A relatively unusual race condition occurs between host software
>> and hardware, where the host sees the updated destination ring head
>> pointer before the hardware updates the corresponding descriptor.
>> When this situation occurs, the length of the descriptor returns 0.
>>
>> The current error handling method is to increment descriptor tail
>> pointer by 1, but 'sw_index' is not updated, causing descriptor and
>> skb to not correspond one-to-one, resulting in the following error:
>>
>> ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1488, expected 1492
>> ath11k_pci 0006:01:00.0: HTC Rx: insufficient length, got 1460, expected 1484
>>
>> To address this problem and work around the broken hardware,
>> temporarily skip processing the current descriptor and handle it
>> again next time. However, to prevent this descriptor from
>> continuously returning 0, use the skb control block (cb) to set
>> a flag. If the length returns 0 again, this descriptor will be
>> discarded.
>>
>> Tested-on: QCA6698AQ hw2.1 PCI WLAN.HSP.1.1-04546-QCAHSPSWPL_V1_V2_SILICONZ_IOE-1
>>
>> Reported-by: Johan Hovold <johan+linaro@kernel.org>
>> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=218623
>> Signed-off-by: Miaoqing Pan <quic_miaoqing@quicinc.com>
> 
>> @@ -387,18 +387,36 @@ static int ath11k_ce_completed_recv_next(struct ath11k_ce_pipe *pipe,
>>   
>>   	ath11k_hal_srng_access_begin(ab, srng);
>>   
>> -	desc = ath11k_hal_srng_dst_get_next_entry(ab, srng);
>> +	desc = ath11k_hal_srng_dst_peek(ab, srng);
>>   	if (!desc) {
>>   		ret = -EIO;
>>   		goto err;
>>   	}
>>   
>>   	*nbytes = ath11k_hal_ce_dst_status_get_length(desc);
> 
> As I mentioned elsewhere, this function also sets the length field in
> the descriptor to zero. So if there's a racing update, you may never see
> the updated length.
> 

Will add below check.

--- a/drivers/net/wireless/ath/ath11k/hal.c
+++ b/drivers/net/wireless/ath/ath11k/hal.c
@@ -602,7 +602,11 @@ u32 ath11k_hal_ce_dst_status_get_length(void *buf)
         u32 len;

         len = FIELD_GET(HAL_CE_DST_STATUS_DESC_FLAGS_LEN, desc->flags);
-       desc->flags &= ~HAL_CE_DST_STATUS_DESC_FLAGS_LEN;
+       /* Avoid setting the length field in the descriptor to zero when 
length
+        * is 0, as there's a racing update, may never see the updated 
length.
+        */
+       if (likely(len))
+               desc->flags &= ~HAL_CE_DST_STATUS_DESC_FLAGS_LEN;



>> -	if (*nbytes == 0) {
>> -		ret = -EIO;
>> -		goto err;
>> +	if (unlikely(*nbytes == 0)) {
>> +		struct ath11k_skb_rxcb *rxcb =
>> +			ATH11K_SKB_RXCB(pipe->dest_ring->skb[sw_index]);
>> +
>> +		/* A relatively unusual race condition occurs between host
>> +		 * software and hardware, where the host sees the updated
>> +		 * destination ring head pointer before the hardware updates
>> +		 * the corresponding descriptor.
>> +		 *
>> +		 * Temporarily skip processing the current descriptor and handle
>> +		 * it again next time. However, to prevent this descriptor from
>> +		 * continuously returning 0, set 'is_desc_len0' flag. If the
>> +		 * length returns 0 again, this descriptor will be discarded.
>> +		 */
>> +		if (!rxcb->is_desc_len0) {
>> +			rxcb->is_desc_len0 = true;
>> +			ret = -EIO;
>> +			goto err;
>> +		}
> 
> If you add the memory barrier and make sure not to clear the length
> field above, do you still see the length sometimes always reading zero
> if you retry more than once (i.e. drop the is_desc_len0 flag)?
> 
> Perhaps the device is really passing you a zero-length descriptor that
> can simply be discarded straight away?
> 
> Johan

Will verify your suggestion, thanks.